Maximizing the first hyperpolarizability (#beta#) of conjugated push-pull charge transfer molecules: Tuning of charge transfer and electron correlation effects

摘要

A two-atom two-orbital huckel like model has been proposed to predict analytically the possible variations of the first hyperpolarizability (#beta#) of intramolecualr organic charge transfer systems when the system parameters change. The model identifies some parameters which can be tuned to achieve the maximization of #beta#. They include donor-acceptor interaction strength (hopping term), donor and acceptor strength (ionization potential of the donor and electron affinity of the acceptor), state of hybridization of the donor orbital, etc. A simple modification of the same basic model that includes electron interaction explicitly throws some light on the possible role of electron correlation in the emergence of high nonlinear optical response when the other system parameters are favourably tuned.